Contaminated Sediments Assessment & Management
Some of the most complicated environmental projects involve sediment sites requiring remediation and restoration, and include multidisciplinary evaluation and management of contaminated sediment systems. Most of these sites are Superfund sites located in urban areas and involve multiple contaminants and numerous responsible parties (RPs). Effectively evaluating and addressing sediment contamination requires a wide range of expertise. Whether representing individual RPs, groups of RPs, or conducting independent research, Exponent’s team of aquatic/marine toxicologists, risk assessors, geochemists, ecologists and engineers strive to pursue environmentally protective and cost-sensitive solutions to complex contaminated sediment problems. Often times this includes determination of liability and allocation of responsibility (see “Divisibility, Apportionment, and Allocation” capabilities). Such solutions rest on fundamental scientific principles that govern the extent to which humans and wildlife may come into contact with and may be affected by different contaminants in these systems.
Exponent has worked on major contaminated sediment sites nationwide, including marine, estuarine, riverine, and large and small lacustrine systems. Examples include: Commencement Bay, San Diego Harbor, Portland Harbor, Coeur d’Alene River, Clark Fork River, Fox River, Kalamazoo River, Saginaw River, Hudson River, Passaic River, Onondaga Lake, Gowanus Canal, Berrys Creek, and many others in the U.S. and overseas. Exponent scientists evaluate key data gaps and then design and oversee sampling and analysis programs, including close scrutiny of data generation activities by contracted laboratories. These data are used to identify the nature and extent of contamination, whether and to what extent various effects may be occurring, and the source of environmental risks. This analysis is used in concert with industry and agencies to determine whether remediation is appropriate and to identify optimal actions. In a litigation setting, field studies may also include an environmental forensics component, which can support allocation. Exponent also develops allocation models using data as well information about historical operations.
Exponent brings experience in understanding and deconvoluting multiparty sediment sites involving polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs), dioxins/furans, pesticides and metals. Exponent’s scientists and engineers participate in national and international panels charged with identifying how best to evaluate and manage sediments, such as the California State Water Resources Control Board advisory committee. We are also an active sponsor of the Sediment Management Work Group (SMWG).
Risk posed by sediment-associated chemicals to aquatic organisms may be understood through evaluating three metrics of sediment quality, known as the Sediment Quality Triad: chemistry, toxicity, and benthic community composition. Measurements of these three areas are integrated to reach conclusions based on the degree of risk indicated by each measurement and the confidence in each measurement. Exponent’s scientists have extensive experience in applying the Sediment Quality Triad approach to sediments across the U.S. Our scientists have specific expertise in cost-effective study design, including selecting appropriate test methods, interpreting results of Sediment Quality Triad studies, and developing technically defensible cleanup goals to support remedial decisions. We also have extensive experience evaluating the health risk posed to human consumers of fish and shellfish exposed to sediment-associated contaminants.
Specific services provided by Exponent’s contaminated sediments team include:
- Human health and ecological risk assessment
- Natural resource damage assessment (NRDA)
- CERCLA and Oil Pollution Act (OPA) consulting
- Design and oversight of field investigations, including those involving field measurement of contaminant bioavailability
- Data optimization
- Data management and spatial analysis, including geographic information systems (GIS)
- Contaminant transport and fate, sediment transport analyses
- Bioavailability and bioaccumulation studies
- Sediment toxicity studies and sediment quality triad assessments
- Environmental forensics investigations
- Remedial alternative analysis (including natural attenuation) and feasibility studies
- Regulatory strategy development
- Remediation and restoration planning and oversight
- Constructed treatment wetlands design
- Ecosystem impact and recovery monitoring.